CO and trans-cinnamaldehyde as corrosion inhibitors of 1825, L80-13Cr and N80 alloys in concentrated HCl solutions at high pressure and temperature

In this paper, corrosion inhibition by chemisorbed CO, at high pressure and temperature, on a high-Ni ferrous alloy (Incoloy 825) and two high-Fe alloys (13Cr-L80 (Uniloy-420) and N80 steels) in very aggressive conditions (15% (w/w) HCl solution) is described. CO was either directly dosed into the electrolyte, or produced by dehydration of formic acid. It is shown that CO is a very good corrosion inhibitor, the inhibiting effect being even higher at high pressure and temperature than at normal pressure and room temperature. The effect of combining CO with a common acid corrosion inhibitor, trans-cinnamaldehyde (TCA), at high pressure and temperature, was also studied. Under these conditions, the polymerization of TCA may be favored, leading to a thin film on the metal surface that appears to serve as a barrier to corrosion. It was found that, when CO is used in combination with TCA, the inhibiting effect of the latter is considerably intensified.